1. Field of the Invention
The present invention relates to a typewriter having a function of automatically erasing a group of successive characters having a certain length, that is, a word, a phrase, or a line of characters, and/or an improved typewriter having a function of continuously erasing successive words which are presented on a suitable data-presentation means such as a display or a recording medium, such that the adjacent words are separated from each other by spaces.
2. Discussion of the Prior Art
Laid-Open Publication No. 60-210482 of Japanese Patent Application discloses a typewriter capable of erasing a word or words. In this typewriter, the operator depresses a word-erase key after a carriage of the typewriter has been positioned at one of characters of a word that the operator wishes to erase. In response to the operation of the word-erase key, the carriage is automatically moved to the last character of the word, and an operation to erase the word is initiated. After the first character of the word has been erased, the erasing operation is automatically terminated. When it is desired to erase a plurality of words, the carriage is moved to the last one of the words, and the word-erase key is operated a plurality of times corresponding to the number of the words to be erased. The typewriter repeats a word erasing cycle in response to the repetitive operations of the word erase key, and the erasing operation is automatically terminated. Also known is a typewriter which has a function of erasing a line of characters by a single depression of a suitable key.
In such a known typewriter capable of automatically erasing a desired length of characters, such as a single word, or a phrase or a line consisting of a plurality of words, a typing job may be achieved efficiently.
In the known typewriter discussed above, however, an erasing operation cannot be stopped or interrupted once the operation has been initiated. The operator often notices an error in designating a portion of a material to be erased, after the erasing operation has been started. In this case, the erasing cycle is automatically repeated until all of the characters of the designated portion of the material have been erased. This is inconvenient, since the operator must wait until the characters which are not actually necessary to erase have been erased, before the typewriter becomes ready for permitting the operator to start keying in the desired data.
For improved typing efficiency, it is desirable to enter data during an automatic erasing operation, so that the thus entered data may be printed after the completion of the erasing operation. If data is erroneously entered during an erasing operation, or if the portion to be erased has been erroneously designated, the data entered during the erasing operation must also be erased after this erroneous data is printed. This extra erasure is time-consuming.
There is also known a typewriter as disclosed in U.S. Pat. No. 3,870,846, wherein an operation to erase a character (letter, numeral or symbol) is automatically repeated while an erase key is held operated. Thus, two or more words may be automatically erased. In this arrangement, therefore, the operator must release the erase key just when the erasure of the last charcter of the last word to be erased is completed.
It is considered possible that once the erase key has been operated, an automatic character erasing operation is repeated until the erase key is again operated. Automatic erasure of a plurality of words is also possible by providing a line-erase key which commands the erasure of a whole line of characters.
While it is preferred to erase the characters at a high speed for improved erasing efficiency, the penalty for this in the above typewriter lies in increased difficulty to manipulate the appropriate key to terminate the erasing operation just when the desired last word to be erased has been erased. In the typewriter equipped with a line-erase key, the operator may sometime notice an erroneous operation of the line-erase key, as soon as the operator has depressed the line-erase key. In this case, a suitable key is preferably operated to cancel or terminate the erasing opeation. However, if the erasing speed is so high, the operation of the key to terminate the operation is delayed, resulting in the erasure of the whole line of characters, which requires re-entry of the erased data.
The above inconveniences may easily be encountered particularly in connection with the erasure of characters being displayed on a display device, since the speed at which the display is cleared is comparatively high. However, the same inconveniences may occur even when the characters printed on a paper are erased, if the erasing speed is relatively high.